A number of frozen food packages are known containing a food portion intended to remain frozen such as frozen desserts and another food portion intended to be thawed, melted or heated. Multi-component containers have also been manufactured with a variety of constructions that allow sections of the container to be exposed to microwave energy while shielding other sections from microwave energy.
U.S. Pat. No. 4,233,325 issued to Slangan et al. discloses one such microwaveable multi-compartment package. This package includes a lower compartment, containing frozen ice cream, which is substantially impermeable to microwave energy and an upper compartment, containing frozen syrup, which is microwave permeable. The package is placed in a microwave oven to melt the frozen syrup in the upper compartment. The two compartments are manufactured from separate cardboard blanks, formed and then fit together. U.S. Pat. No. 4,794,008 issued to Schmidt et al describes an upper frozen food compartment permeable to microwave energy formed from plastic and a lower frozen food compartment constructed from a microwave reflective material such as foil. The compartments are formed into U-shaped plastic compartments and joined together to form a single multi-compartment food package. The two compartments must be further separated from one another after heating in order to access the food contained within the compartments.
U.S. Pat. No. 4,081,646 issued to Goltsos discloses a multi-compartment heating container including a tray and cover that is thermo-formed from plastic which is transparent to microwave energy. The outer surfaces of the tray and cover may be shielded against the microwave energy by a thin film of radiation-opaque material, except for regions which are intended to define microwave-transparent openings. Each compartment in this container is shielded against different amounts of microwave energy by leaving different sized windows on each compartment free from the radiation-opaque material. U.S. Pat. No. 5,718,370 also discloses a partially shielded microwave heating container having a first compartment shielded from microwave energy and a second compartment permeable by microwave energy. The first compartment includes a layer of microwave shielding material laminated to a portion of the sheet of microwave permeable paperboard material that forms the container.
U.S. Pat. No. 4,894,503 discloses packaging materials for heating food in a microwave oven that includes metal shielding or other metal components which cause a gain in electric field strength that is greater than 3. Preferably, the packaging is formed from high density polyethylene or polypropylene or co-polymers thereof. U.S. Pat. No 4,926,020 discloses a method and food product structure that allows for the controlled heating of multi-component foods in a microwave oven. A layer of an edible substance with preselected properties and positioned adjacent to one or more food items is used as a shield to control the amount of transmitted microwave power to the adjacent food.
In-mold labeling methods and apparatus are also known. For example, U.S. Pat. Nos. 5,104,306; 5,121,913 and 5,256,365 all describe methods and apparatus for labeling mold cavities in blow-molding machines. U.S. Pat. No. 4,904,324 discloses a method of making and labeling a plastic container by applying the label during the blow molding of the plastic container. A multilayer label is positioned in a mold cavity with the outer layer of the label in contact with the mold. During the molding process, the non-cellular inner layer of the label becomes bonded to the outer surface of the container. EP 0492052 describes a method of producing an in-mold labeled vessel having an elongated bottom projection integral with the vessel bottom. The label of this method has a bottom portion and wall portions that cover essentially the entire outside surface of the vessel.
U.S. Pat. No. 4,076,790 discloses a method of incorporating a pre-cut foil sheet in a container injection molded from thermoplastic material. The foil sheet can be located on either the inner surface or outer surface of the container to serve as a diffusion barrier or label. The foil sheet can completely cover the inside or outside of the container, it can cover the bottom and two opposing sides of the container, or it can cover the bottom, two opposing sides and one-half of the remaining two opposing sides. U.S. Patent Application Publication U.S. 2001/0019861 describes a laminated decorative sheet for in-mold decorating injection molding. The laminated decorative sheet has a resin layer containing an acrylic-modified polyolefin resin that is placed into contact with an injection-molded resin molding. The decorative sheet covers the outer surface of a resin mold object. WO 02/062552 describes a method for manufacturing a diffusion-tight plastic container using a film material having barrier properties. The film material label is pre-cut and pre-shaped prior to placing the label into a mold that has an inner surface corresponding to the outer surface of the plastic container to be manufactured. The label forms the outer surface of the container. The above references are fully incorporated herein by reference.
It would be desirable to have a container that includes a microwave permeable section and a microwave shielded section, formed from a single rigid or semi-rigid container that is configured to provide for at least a susceptor and a shielding zone.
Another object of the present invention is to provide a single rigid or semi-rigid container formed by molding technology in which the container has at least a section that is permeable by microwave energy and at one other section that is reflective to microwave energy that utilizes in-mold labeling systems to provide for the susceptor and a shielding zones.
It is yet another object of the present invention is to provide a microwave heating container partially shielded against microwaves that is formed from a single rigid or semi-rigid mold with a microwave reflective material incorporated on only a portion of the mold.
It would also be advantageous to provide a single rigid or semi-rigid container formed by molding technology in which the container has at least one section that is permeable by microwave energy and at least one other section that is reflective to microwave energy in which the container, upon being opened, can also be used to hold the food product while being eaten.